﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LTKJ.RTU
{
    class Crc16
    {

        public static ushort[] CRC16Table =
          {
                0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
                0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
                0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E,
                0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
                0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD,
                0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
                0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C,
                0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
                0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB,
                0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
                0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A,
                0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
                0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9,
                0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
                0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738,
                0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
                0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7,
                0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
                0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036,
                0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
                0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5,
                0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
                0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134,
                0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
                0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3,
                0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
                0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232,
                0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
                0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1,
                0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
                0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330,
                0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,
               };


        /// <summary>
        /// 计算得到CRC-16校验
        /// </summary>
        /// <param name="data"></param>
        /// <param name="byteLen"></param>
        /// <returns></returns>
        public static byte[] crc16_bytes(byte[] data, int byteLen)
        {
            int xda, xdapoly;
            int i, j, xdabit;
            xda = 0xFFFF;
            xdapoly = 0xA001;

            for (i = 0; i < byteLen; i++)
            {
                xda ^= data[i];
                for (j = 0; j < 8; j++)
                {
                    xdabit = (int)(xda & 0x01);
                    xda >>= 1;
                    if (xdabit == 1)
                        xda ^= xdapoly;
                }
            }

            byte[] outBytes = { (byte)(xda & 0xff), (byte)(xda >> 8) };
            return outBytes;
        }


        /// </summary>
        /// <param name="data">待校验数组</param>
        /// <param name="data_Len">待校验数组的长度</param>
        ///  /// <returns>返回校验结果</returns>
        public static int CRC16_CCITT(Byte[] data, int data_Len)
        {
            int crc = 0xffff;
            int i = 0;
            while ((data_Len--) > 0)
            {
                //data[i] = Convert.ToUInt16(data[i]);
                crc = (crc >> 8) ^ Crc16.CRC16Table[(crc ^ data[i]) & 0xff];
                i++;
            }
            crc ^= 0xFFFF;    
            return crc;
        }

        /// <summary>
        /// 计算给定长度数据的16位CRC
        /// </summary>
        /// <param name="data">要计算CRC的字节数组</param>
        /// <returns>CRC值</returns>
        public static UInt16 GetCrc16(Byte[] data)
        {   // 初始化
            Int32 High = 0xFF;  // 高字节
            Int32 Low = 0xFF;   // 低字节
            if (data != null)
            {
                foreach (Byte b in data)
                {
                    Int32 Index = Low ^ b;
                    Low = High ^ CRC16TABLE_LO[Index];
                    High = CRC16TABLE_HI[Index];
                }
            }

            return (UInt16)(~((High << 8) + Low));    // 取反
        }

        /// <summary>
        /// CRC16查找表高字节
        /// </summary>
        private static readonly Byte[] CRC16TABLE_HI =
        {
            0x00, 0x11, 0x23, 0x32, 0x46, 0x57, 0x65, 0x74, 0x8C, 0x9D, 0xAF, 0xBE, 0xCA, 0xDB, 0xE9, 0xF8,
            0x10, 0x01, 0x33, 0x22, 0x56, 0x47, 0x75, 0x64, 0x9C, 0x8D, 0xBF, 0xAE, 0xDA, 0xCB, 0xF9, 0xE8,
            0x21, 0x30, 0x02, 0x13, 0x67, 0x76, 0x44, 0x55, 0xAD, 0xBC, 0x8E, 0x9F, 0xEB, 0xFA, 0xC8, 0xD9,
            0x31, 0x20, 0x12, 0x03, 0x77, 0x66, 0x54, 0x45, 0xBD, 0xAC, 0x9E, 0x8F, 0xFB, 0xEA, 0xD8, 0xC9,
            0x42, 0x53, 0x61, 0x70, 0x04, 0x15, 0x27, 0x36, 0xCE, 0xDF, 0xED, 0xFC, 0x88, 0x99, 0xAB, 0xBA,
            0x52, 0x43, 0x71, 0x60, 0x14, 0x05, 0x37, 0x26, 0xDE, 0xCF, 0xFD, 0xEC, 0x98, 0x89, 0xBB, 0xAA,
            0x63, 0x72, 0x40, 0x51, 0x25, 0x34, 0x06, 0x17, 0xEF, 0xFE, 0xCC, 0xDD, 0xA9, 0xB8, 0x8A, 0x9B,
            0x73, 0x62, 0x50, 0x41, 0x35, 0x24, 0x16, 0x07, 0xFF, 0xEE, 0xDC, 0xCD, 0xB9, 0xA8, 0x9A, 0x8B,
            0x84, 0x95, 0xA7, 0xB6, 0xC2, 0xD3, 0xE1, 0xF0, 0x08, 0x19, 0x2B, 0x3A, 0x4E, 0x5F, 0x6D, 0x7C,
            0x94, 0x85, 0xB7, 0xA6, 0xD2, 0xC3, 0xF1, 0xE0, 0x18, 0x09, 0x3B, 0x2A, 0x5E, 0x4F, 0x7D, 0x6C,
            0xA5, 0xB4, 0x86, 0x97, 0xE3, 0xF2, 0xC0, 0xD1, 0x29, 0x38, 0x0A, 0x1B, 0x6F, 0x7E, 0x4C, 0x5D,
            0xB5, 0xA4, 0x96, 0x87, 0xF3, 0xE2, 0xD0, 0xC1, 0x39, 0x28, 0x1A, 0x0B, 0x7F, 0x6E, 0x5C, 0x4D,
            0xC6, 0xD7, 0xE5, 0xF4, 0x80, 0x91, 0xA3, 0xB2, 0x4A, 0x5B, 0x69, 0x78, 0x0C, 0x1D, 0x2F, 0x3E,
            0xD6, 0xC7, 0xF5, 0xE4, 0x90, 0x81, 0xB3, 0xA2, 0x5A, 0x4B, 0x79, 0x68, 0x1C, 0x0D, 0x3F, 0x2E,
            0xE7, 0xF6, 0xC4, 0xD5, 0xA1, 0xB0, 0x82, 0x93, 0x6B, 0x7A, 0x48, 0x59, 0x2D, 0x3C, 0x0E, 0x1F,
            0xF7, 0xE6, 0xD4, 0xC5, 0xB1, 0xA0, 0x92, 0x83, 0x7B, 0x6A, 0x58, 0x49, 0x3D, 0x2C, 0x1E, 0x0F
        };

        /// <summary>
        /// CRC16查找表低字节
        /// </summary>
        private static readonly Byte[] CRC16TABLE_LO =
        {
            0x00, 0x89, 0x12, 0x9B, 0x24, 0xAD, 0x36, 0xBF, 0x48, 0xC1, 0x5A, 0xD3, 0x6C, 0xE5, 0x7E, 0xF7,
            0x81, 0x08, 0x93, 0x1A, 0xA5, 0x2C, 0xB7, 0x3E, 0xC9, 0x40, 0xDB, 0x52, 0xED, 0x64, 0xFF, 0x76,
            0x02, 0x8B, 0x10, 0x99, 0x26, 0xAF, 0x34, 0xBD, 0x4A, 0xC3, 0x58, 0xD1, 0x6E, 0xE7, 0x7C, 0xF5,
            0x83, 0x0A, 0x91, 0x18, 0xA7, 0x2E, 0xB5, 0x3C, 0xCB, 0x42, 0xD9, 0x50, 0xEF, 0x66, 0xFD, 0x74,
            0x04, 0x8D, 0x16, 0x9F, 0x20, 0xA9, 0x32, 0xBB, 0x4C, 0xC5, 0x5E, 0xD7, 0x68, 0xE1, 0x7A, 0xF3,
            0x85, 0x0C, 0x97, 0x1E, 0xA1, 0x28, 0xB3, 0x3A, 0xCD, 0x44, 0xDF, 0x56, 0xE9, 0x60, 0xFB, 0x72,
            0x06, 0x8F, 0x14, 0x9D, 0x22, 0xAB, 0x30, 0xB9, 0x4E, 0xC7, 0x5C, 0xD5, 0x6A, 0xE3, 0x78, 0xF1,
            0x87, 0x0E, 0x95, 0x1C, 0xA3, 0x2A, 0xB1, 0x38, 0xCF, 0x46, 0xDD, 0x54, 0xEB, 0x62, 0xF9, 0x70,
            0x08, 0x81, 0x1A, 0x93, 0x2C, 0xA5, 0x3E, 0xB7, 0x40, 0xC9, 0x52, 0xDB, 0x64, 0xED, 0x76, 0xFF,
            0x89, 0x00, 0x9B, 0x12, 0xAD, 0x24, 0xBF, 0x36, 0xC1, 0x48, 0xD3, 0x5A, 0xE5, 0x6C, 0xF7, 0x7E,
            0x0A, 0x83, 0x18, 0x91, 0x2E, 0xA7, 0x3C, 0xB5, 0x42, 0xCB, 0x50, 0xD9, 0x66, 0xEF, 0x74, 0xFD,
            0x8B, 0x02, 0x99, 0x10, 0xAF, 0x26, 0xBD, 0x34, 0xC3, 0x4A, 0xD1, 0x58, 0xE7, 0x6E, 0xF5, 0x7C,
            0x0C, 0x85, 0x1E, 0x97, 0x28, 0xA1, 0x3A, 0xB3, 0x44, 0xCD, 0x56, 0xDF, 0x60, 0xE9, 0x72, 0xFB,
            0x8D, 0x04, 0x9F, 0x16, 0xA9, 0x20, 0xBB, 0x32, 0xC5, 0x4C, 0xD7, 0x5E, 0xE1, 0x68, 0xF3, 0x7A,
            0x0E, 0x87, 0x1C, 0x95, 0x2A, 0xA3, 0x38, 0xB1, 0x46, 0xCF, 0x54, 0xDD, 0x62, 0xEB, 0x70, 0xF9,
            0x8F, 0x06, 0x9D, 0x14, 0xAB, 0x22, 0xB9, 0x30, 0xC7, 0x4E, 0xD5, 0x5C, 0xE3, 0x6A, 0xF1, 0x78
        };

    }
}
